Blast proof mines

ABSTRACT

1. In a mine adapted to be implanted in the soil, said mine including an explosive charge and a cavity therethrough; an upwardly biased active member slidably mounted in said cavity; a downwardly biased preventive pressure member slidably mounted in said cavity, said preventive pressure member having a greater area than said active member; a firing mechanism for exploding said mine mounted in said mine and adapted to be activated by said active member upon a downward pressure applied thereon, and said preventive pressure member acting upon an air blast above the soil to prevent said active member from activating said firing mechanism.

United States Patent [1 1 Clemens et al.

[ May 13, 1975 1 1 BLAST PROOF MINES [75] Inventors: John Ewart Clemens, Xenia; Ben B.

Johnstone, Dayton, both of Ohio; Heinz E. Strohmeyer, Beverly, Mass.

[73] Assignee: The United States of America as represented by the Secretary of the Army, Washington, DC.

[22] Filed: Dec. 23, 1960 [21] Appl. No.: 78,191

[52] U.S. Cl. 102/8; 102/17; 102/70 [51] Int. Cl F421) 23/04 [58] Field of Search 102/7, 8, 70, 9, 10, 81, 102/82, 17

[56] References Cited UNITED STATES PATENTS 2,555,318 6/1951 Christensen 102/8 2,678,604 5/1954 Walker 102/8 2,857,842 10/1958 Malm...... 102/70 Primary ExaminerBenjamin A. Borchelt Assistant Examiner-H. .1. Tudor Attorney, Agent, or FirmRobert R Gibson; Nathan Edelberg EXEMPLARY CLAIM 1. In a mine adapted to be implanted in the soil, said mine including an explosive charge and a cavity therethrough; an upwardly biased active member slidably mounted in said cavity; a downwardly biased preventive pressure member slidably mounted in said cavity,

said preventive pressure member having a greater area than said active member; a firing mechanism for exploding said mine mounted in said mine and adapted to be activated by said active member upon a downward pressure applied thereon, and said preventive pressure member acting upon an air blast above the soil to prevent said active member from activating said firing mechanism.

2 Claims, 9 Drawing Figures PHTENTED MAY 1 (N875 3.882.776

SHEEI 10F 3 John E Clemens By Ben E1 .Jmhhstune' Heinz Efiirnhmager' MAQLQ-J.

mgmgnm 3197s 3.882.776

sum 2 or 3 INVENTORS, Jul-Ln. E C1Emen 5 By Ben ElJuhnstul-la Heinz Efihuhmeyer PATENTEDHAY 1 m 882.776

SHEET 3 OF 3 INVENTOR5. Jcl'hn E. Clemens BY Ben. E1. Juhns'tune Heinz Efiiruhmeger' i/QJM a: 9445M BLAST PROOF MINES This invention relates to a device which is capable of responding when a force of one type is applied thereto, yet which locks and will not respond when a different type of force is applied.

In particular, this invention relates to explosive military mines which will be exploded by a mass-induced pressure, such as a land vehicle will exert, but which will not be affected by pressure from an air-blast.

In the past, it has been the practice to render ineffective a mined area by creating air blasts over the field, and in this manner causing numerous momentary high pressure areas over it. The resulting high pressure would affect the conventional mines in much the same manner as weight, and consequently the mines of the field would be blown up and the field cleared for crossing without any loss of personnel and equipment.

It is the object of this invention to provide a device for a mine which will differentiate between an air-blast induced load and a mass-induced load, thereby making possible a mine which is not vulnerable to defeat by existing mine clearing devices such as by blasting or a projected line charge.

It is also an object of this invention to provide a means to lock out of operation the firing system of a mine while it is under the influence of an explosive air blast, yet leaving the mine free to be exploded by signatures generated by a land vehicle.

The blast-proof mine firing mechanismdescribed in detail hereinafter rests on the concept of differences of transmittal through soil of an air-blast induced pressure as opposed to a mass-induced pressure.

The basic principle of operation relies on the fact that an air pressure generated above the ground and exerted upon thesoil surface is mainly transmitted as a uniform air pressure wave through the voids between soil particles and has therefore the same magnitude in all directions and on all exterior surfaces of a mine, regardless of location as long as the location is accessible to the pressure. This is true irrespective of the plane in which the mine parts are laid relative to the soil surface; the air-blast pressure is transmitted through the soil and is substantially uniform in all directions. Furthermore, the pressure is transmitted through the soil without any appreciable time delay in any type of soil having at least a consistency such that it can support a mechanical load of 1 pound per square inch; this insures operability of the principle where the mean surface pressure of a man or a tank is involved.

The operation of the instant invention also relies on the principle that a mass-induced pressure on the soil surface is transmitted mainly by the soil particles and creates therefore different pressure values in different directions with the main force being directed downward. This latter mode of pressure transmittal permits shielding of mine parts from this substantially unidirectional pressure. Shielding can be accomplished in several ways. An air gap or air space between the load and the part to be shielded can be successfully employed. Or a grid between the source of the pressure and the mine part may be used; so long as the grid has sufficient structural rigidity to withstand the load and also has sufficient openings to transmit air pressures.

Utilization of the aforesaid principles are herein presented in four different devices, as shown in the accompanying drawings. Each device has in common a fuze with a restrained firing pin, an active weight member which is actuated by any type of soil pressure and which, if uninhibited, releases the firing pin as soon as the pressure exceeds a predetermined magnitude, and also a preventive pressure member which counteracts the active weight member and prevents release of the firing pin if a pressure of the same magnitude is applied thereto. The preventive pressure member is situated in such a manner in each of the devices that a mass-induced pressure thereon will be of a considerably smaller magnitude than the simultaneous pressure on the active member. The four devices differ from one another in their structure and in the method by which the pressure reduction is achieved.

In accordance with the foregoing, the instant inven-- tion will now be described with reference to the accompanying drawings wherein:

FIG. 1 is a sectional view of a mine having a preventive pressure plate in the bottom and shown under no load conditions;

FIG. 2 is a sectional view of the mine under a mechanical load;

FIG. 3 is a sectional view of the mine under a load generated by an air blast;

FIG. 4 is a sectional view of a mine having a preven-. tive pressure plate mounted in the side thereof;

FIG. 5 is a sectional view of a mine having a screened chest cavity;

FIG. 6 is an auxilliary perspective view showing details of the mine shown in FIG. 5;

FIG. 7 illustrates the mine of FIG. 5 when it is subjected to a mechanical load;

FIG. 8 is a sectional view of a mine having a gridcovered preventive pressure plate; and

FIG. 9 illustrates the mine of FIG. 8 when it is subjected to a mechanical load.

Referring more particularly to the drawings wherein like reference characters designate like or corresponding parts throughout the different views and referring more particularly to FIG. 1, there is shown an explosive charge 11 in a mine generally designated 12. This device depends for operation on the fact that the amount of soil pressure, created by a mass-induced surface pressure, is quite different in different directions. The mine 12 is cylindrically shaped and has in the upper side 13 thereof a cylindrical cavity 14 defined by the side 15 and in the under side thereof another recessed cylindrical cavity 16 defined by the sides 17 and 18. The underside cavity 16 is of larger diameter than the cavity 14. The bottom of the mine is supported by legs as at 19. The active weight member 20 is a plate slidably mounted in the conventional manner in the cavity 14, and it projects outwardly from the top surface 13 of the mine 12. The active weight member 20 acts against a Belleville Spring 21 biased between the underside thereof and a rigidly-fixed center plate 22. The underside of the active weight member 20 is provided with a raised centerpoint 23 which can pass through an opening 24 in the centerplate 22. A preventive pressure member 25 is located in the recessed cavity 16 in opposite arrangement to the active weight member. This preventive pressure member 25 is further provided with a raised centerpoint 26 and is biased by a Belleville Spring 27 so that it maintains the position shown in FIG. 1 under no load conditions. Disposed in the mine 12 is a firing pin 28 which is biased by a spring 29 so that it tends to stab into a booster charge 30. However, it is restrained from doing so by a lever 31 which extends into the cavity 14, the lever being rotatable about a pivot pin 32.

In operation, when a mass-induced pressure is exerted, such as by a tank as shown in FIG. 2, the force transmitted through the soil is not uniformly directed, but rather approaches that of a uni-directional force acting downwardly upon the outwardly projecting active weight member 20. This will drive it down into the cavity 14 against the opposing force of the spring 21 thereby tripping the lever 31 and releasing the spring biased firing pin 28.

FIG. 3 illustrates the effect of an air blast on the device. The air pressure that is exerted upon the soil covering the mine will be transmitted in a uniform manner through the voids of the soil and will consequently exert a force upon both the active weight member 20 and the preventive pressure member 25. Since the area of the preventive pressure member 25 is larger than that of the active weight member 20, when the uniform pressure causes each plate to deflect their respective Belleville Spring, the preventive pressure member 25 will exert more force and consequently deflect its respective spring 27 more. As seen in FIG. 3, the raised center post 26 carried by the preventive pressure member will consequently meet the corresponding raised center post 23 of the active weight member and, when this happens, further downward movement of the active weight member is prevented, so the firing pin will continue to be restrained.

FIG. 4 depicts another device utilizing the principle of operation employed in FIGS. 1 3. The preventive pressure member 25 is disposed in the side of the mine and is labeled 25, as it was in FIG. 1 since it again acts as the preventive member in that it is unaffected by mass-induced pressure to the extent that it is by a uniform air pressure. The structural arrangement in this device of the active weight member 20 with its associated centerpost 23 and spring 21, remains the same as in the foregoing device, as do the firing pin 28 and lever 31. The preventive pressure member 25 again actuates a centerpost 26 to which it is connected through the intermediary of a toggle 33 and an actuator rod 34. Pressure applied to the preventive pressure member 25 will be transmitted through the rod and toggle, raising the centerpost 26. The preventive pressure member 25 is housed in a suitable recess 16 in the side of the mine and is provided with a Belleville spring 27, as shown.

In light of the previous operation description, it is sufficient to point out that a uniform sub-surface pressure will exert a force on the preventive pressure member 25 which will be transmitted through the rod and toggle to the centerpost 26. The centerpost 26 will move up within the piston cylinder 35 and engage the centerpost 23 and thus prevent the active weight member 20 from tripping the lever 31 to explode the mine. This type of design does not require that the mine be supported by legs encompassing a recess; hence it can be laid in the conventional manner with operating parts accessible from the side or top.

The mine illustrated in FIGS. 7 is based on the previously described principles and particularly on the fact that an air space will not transmit a mass-induced pressure. The force produced by a mass-induced pressure relies upon soil particles to conduct it; and it will not be transmitted by an air space alone. However, an air space will readily transmit air pressure. FIG. 5 illustrates this type mine. It has an explosive 11, an outwardly projecting active weight member 20, a preventive pressure member 25 and a spring biased firing pin 28, restrained from stabbing into a detonator 30. The active weight member consists of a grid which is covered by a screen or cloth 44 so that air, but not soil, can get through to the preventive pressure member 25. The preventive pressure member is located centrally under the active weight member 20, and it can be made to move upward against the force of the Belleville Spring 36. As clearly shown in FIG. 6, both members, the active 20 and the preventive 25, are connected by a balancing linkage system which comprises a balance link 37 pivotably mounted at its center to a center support 38. At one end of the balance link, there is pivotably mounted a link 39, which is linked at the other end to the active member 20. The opposite end of the balance link 37 is fastened to a restraining element 40. The restraining element is cylindrically shaped and is disposed between the preventive pressure member 25 and the bottom 41 of the mine. Housed within and restrained by the cylindrical restraining element is the firing pin 28, which is biased so that it tends to plunge through an opening 42, provided in the restraining element, and stab into the detonator 30.

In operation a uniform air pressure will not cause the restraining element 40 to move upward, and permit the opening 42 to become large enough for the firing pin 28 to plunge through. This inactivity results because both the active weight member 20 and the preventive pressure member 25 are connected to the balancing link 37 at opposive ends thereof, and they counter balance one another. The force of the air blast will be transmitted through the screen 44 into the chest cavity 45 and exert a downward force on the preventive pressure member 25 thereby holding the firing pin 28 in place against the effect of the counter weighting, but smaller, force of the active weight member 20. In short, when a uniform air pressure wave strikes the device, no movement of the restraining element will occur, since forces on the preventive pressure member will more than cancel the force on the active weight member.

The effect of a mass-induced pressure is illustrated in FIG. 7. It will create a downward force on the active weight member 20 which is not balanced. Consequently this force will be transmitted through the linkage balancing system, 39, 37, 40, and cause the restraining element 40 to be raised up against the force of the spring 36. The tension of the spring member 36 may be pre-set and thus a force magnitude which will initiate the explosive can be preselected.

The fourth type of mine is illustrated in FIGS. 8 and 9. In this device the chest cavity of FIG. 5 is not required because a feature of this device is that the necessity of an air transport into the entrapped air space is obviated. The operation of this device is based on the principle that a mechanical load, which is supported by a combination of a stiff and a weak spring will be distributed proportional to the stiffness of the two springs. As best seen in FIG. 8, the preventive pressure member 25 consists of a ring shaped movable pressure plate beneath a grid 46 rigidly fixed to the mine top 13 and having relatively narrow openings therein. The preventive pressure member 25 is slidably mounted in the cavity defined by the sides 47 and 48 and has attached thereto a link 39. A balancing link 37 is centered on a center support 38, and the link 39 is pivotably connected to one end of the balance link 37. The other end of the balance link is provided with a pivot pin 49. The active member is slidably disposed in a centrally located cavity 14. The active member is provided with a centerpost 23 which is fastened to the pivot pin 49, and it is spring biased so that it projects above the top surface l3 of the mine 12. Disposed beneath the pivot pin 49 is a lever 31 rotatable about a pin 32. This lever in the normal position, as seen in FIG. 8, engages and restrains the spring biased firing pin 28.

In operation, because the grid sturdily supports a mechanical load and resists deformation, any weight over the grid 46 will be supported mainly by the grid and exert no or almost no pressure on the preventive pressure member 25. However, since the active plate 20 projects above the solid surface of the mine, it will bear the brunt of a mechanical load yielding and thus depressing its center post 23. The center post will pivot the firing pin restraining lever 31 releasing the firing pin 28. This is clearly shown in FIG. 9. An air pressure, however, would exert a countervailing force on the preventive pressure member which would be at least equal in magnitude to the force on the active member. in this case the link 37 would be balanced and prevent the center post 23 from being depressed and releasing the firing pin. This results because the grid 46 permits the air pressure to be readily transmitted through it, and as regards the air pressure it acts as if no grid were present. The grid is required, however, in order to isolate the preventive pressure member 25 from any applied loads.

It should be noted that the relative sizes of a tank and a mine as shown in the drawings are out of proportion with respect to each other. The mine and its associated parts are considerably enlarged for the purpose of clarity in the description of the invention.

While the invention has been shown and described herein in certain preferred embodiments, it will be recognized that departures may be made therefrom within the scope of the appended claims.

We claim:

1. In a mine adapted to be implanted in the soil, said mine including an explosive charge and a cavity therethrough; an upwardly biased active member slidably mounted in said cavity; a downwardly biased preventive pressure member slidably mounted in said cavity, said preventive pressure member having a greater area than said active member; a firing mechanism for exploding said mine mounted in said mine and adapted to be activated by said active member upon a downward pressure applied thereon, and said preventive pressure member acting upon an air blast above the soil to prevent said active member from activating said firing mechanism.

2. A mine as set forth in claim 1 wherein said firing mechanism for exploding said mine comprises a detonator; a spring restrained firing pin; and a tripping lever normally restraining said pin in a cocked position, said lever extending into the path of said active member whereby when said active member is urged downward, said lever is pushed down by said active member to release said pin to fire said detonator. 

1. In a mine adapted to be implanted in the soil, said mine including an explosive charge and a cavity therethrough; an upwardly biased active member slidably mounted in said cavity; a downwardly biased preventive pressure member slidably mounted in said cavity, said preventive pressure member having a greater area than said active member; a firing mechanism for exploding said mine mounted in said mine and adapted to be activated by said active member upon a downward pressure applied thereon, and said preventive pressure member acting upon an air blast above the soil to prevent said active member from activating said firing mechanism.
 2. A mine as set forth in claim 1 wherein said firing mechanism for exploding said mine comprises a detonator; a spring restrained firing pin; and a tripping lever normally restraining said pin in a cocked position, said lever extending into the path of said active member whereby when said active member is urged downward, said lever is pushed down by said active member to release said pin to fire said detonator. 